The candidate?s long-term goal is to develop an independent research career to understand risk factors for the development of externalizing behavior over the lifespan. The proposed training plan outlines four objectives critical to achieving this goal: 1) extend expertise in the acquisition and analysis of psychophysiological variables, 2) obtain research experience with young children, 3) obtain training in statistical techniques to test for mediation/moderation, and 4) gain practical skills for research independence. Oppositional defiant disorder (ODD) is prevalent in preschool age children, and its presence substantially increases the risk of developing a full range of other psychiatric disorders. Prior work has differentiated dimensions of ODD (irritability, defiance, vindictiveness) that show differential relationships with later psychopathology; however, the dimensions are highly correlated. Thus, children with oppositionality have similar phenotypic presentations despite being a heterogeneous group with differing longitudinal trajectories. It is proposed that phenotypic symptoms mask the underlying processes that carry differential risks, and that opposing processes in arousal/regulation and social processes systems can lead to both phenotypically similar presentations and explain differences in longitudinal development. Three specific aims are proposed: 1) Identify opposing arousal/regulation processes that differentiate irritability and vindictiveness. 2) Identify opposing social processes that differentiate irritability and vindictiveness. 3) Examine the combined effects of arousal/regulation and social processes in predicting irritability and vindictiveness. It is expected that defiance will be highly correlated with both irritability and vindictiveness, explaining phenotypic similarity. The applicant will accomplish these aims by assessing 175 4-6 year-old children in the greater New Orleans area identified as having behavioral problems. Assessments will include indices of arousal/regulation (pre-ejection period, heart rate variability, and electrodermal response) during baseline or an emotion induction task, and indices of social processes (accuracy and bias in facial emotion recognition). The proposed research will take place at Tulane University in New Orleans, LA and the Child Counseling Associates clinic in Metairie, LA. The anticipated outcome is that irritability will be related to high physiological arousal and an attentional bias toward negative emotional stimuli, whereas vindictiveness will be related to low physiological arousal and deficient emotional recognition abilities. It is expected that these opposing processes will account for the differential relationships with comorbid psychopathology. These results would have the potential to aid the development of individualized interventions to reduce risk for later psychopathology associated with childhood oppositionality. Thus, the proposed research is in line with the high priority goal to identify mechanisms that confer vulnerability to psychiatric illnesses and develop early interventions for reducing the severity and incidence of psychopathology.